1. Field of the Invention
The present invention relates to an oil air lubricating apparatus, and particularly to an oil air lubricating apparatus for carrying lubricating oil, by air, into the inside of rolling bearings for rotatably supporting a high-speed rotating shaft such as a main shaft of a machine tool, or the like.
2. Description of the Related Art
A machine-tool main shaft rotates at a high speed in use. Accordingly, not only a main shaft of this type is required to be rotatably supported by rolling bearings but also a required minimum quantity of lubricating oil is necessary to be accurately supplied to the inside of the rolling bearings when the main shaft rotates. As an apparatus for supplying lubricating oil to the inside of each rolling bearing in the aforementioned manner, an oil air lubricating apparatus conventionally known is configured such that lubricating oil is fed into the inside of a supply passage so as to be carried through the supply passage by air so that the lubricating oil is supplied to a plurality of portions to be lubricated through a plurality of branch passages branched from the aforementioned supply passage. As such an oil air lubricating apparatus, for example, known are those disclosed in German Patent No. 2844995 and Japanese Patent Publication No. Hei. 5-340499. In those oil air lubricating apparatuses, a proper quantity of lubricating oil can be supplied to portions to be lubricated without being affected by the gravity. FIG. 9 shows the oil air lubricating apparatus disclosed in Japanese Patent Publication No. Hei. 5-340499 as one of those known oil air lubricating apparatuses.
The oil air lubricating apparatus disclosed in Japanese Patent Publication No. Hei. 5-340499 is designed to supply lubricating oil to respective portions to be lubricated, that is, multi-row tapered roller bearing 3 for supporting a rotation shaft 2 so as to be rotatable relative to a housing 1, and contact-type oil seal 4, 4 provided on axially opposite sides of the tapered roller bearing 3. This lubricating oil is of an oil air type in which lubricating oil is carried, by air, from a not-shown oil supply source to the aforementioned portions to be lubricated. To this end, a plurality of branch passages 7a, 7b, 7c and 7d are provided in the housing 1, a collar 5 fixedly connected to the housing 1, and a cover 6; and the respective one ends (lower ends in FIG. 9) of the plurality of branch passages 7a, 7b, 7c and 7d are communicated with the aforementioned portions to be lubricated correspondingly. Among the branch passages 7a, 7b, 7c and 7d, the other ends (upper ends in FIG. 9) of the branch passages 7a, 7b and 7c are opened in lower portions of the inner circumferential surface of a support hole 8 provided in the housing 1 while the residual branch passage 7d is opened in the rear end surface of the support hole 8.
A plurality of circular-pipe-like oil supply passages 9, 9 and a plurality of distributors 10a, 10b and 10c are inserted in the inside of the support hole 8, and the plurality of circular-pipe-like oil supply passages 9, 9 and the plurality of distributors 10a, 10b and 10c are arranged axially serially and alternately so that the inner portions of the passages 9, 9 and distributors 10a, 10b and 10c are communicated with one another. Further, each of the distributors 10a, 10b and 10c has a first through-hole 11 for communicating axially-opposite end surfaces with each other, and a second through-hole 12 for communicating one end with one axial end surface (left end surface in FIG. 9) and the other end with the outer circumferential surface. In the condition in which the distributors 10a, 10b and 10c are disposed in the inside of the support hole 8, other-end openings of the second through-holes 12 are matched with other-end openings of the branch passages 7a, 7b and 7c, respectively. The first through-hole 11 provided in the most downstream side distributor 10c is communicated with the branch passage 7d opened in the rear end surface of the support hole 8.
Further, cylindrical sleeves 13 are disposed, as shown in FIG. 10, in portions inside the circular-pipe-like oil supply passages 9, 9 and just prior to the distributors 10a, 10b and 10c respectively. Each of the sleeves 13 has a plurality of slits 14, 14 arranged circumferentially, and a plurality of protrusions 15, 15 provided so as to be protruded from the outer circumferential surface of the sleeve 13. In the condition in which the sleeves 13, 13 are fitted into the circular-pipe-like oil supply passages 9, 9 respectively, cylindrical fine gaps are formed between the outer circumferential surfaces of the sleeves 13, 13 and the inner circumferential surfaces of the circular-pipe-like oil supply passages 9, 9 by the presence of the protrusions 15, 15.
According to the oil air lubricating apparatus disclosed in Japanese Patent Publication No. Hei. 5-340499 and configured as described above, lubricating oil discharged from the not-shown oil supply source can be distributed, in a proper quantity each time, to the branch passages 7a, 7b, 7c and 7d and to portions to be lubricated which are communicated with the branch passages 7a, 7b, 7c and 7d through the circular-pipe-like oil supply passages 9, 9 and the distributors 10a, 10b and 10c, respectively. Further, because cylindrical fine gaps are formed in portions just prior to the distributors 10a, 10b and 10c by the presence of the sleeves 13, lubricating oil flowing in the fine gaps is spread circumferentially by capillarity even in the case where the quantity of lubricating oil flowing in the circular-pipe-like oil supply passages 9, 9 is so small that the lubricating oil is reserved in lower portions of the circular-pipe-like oil supply passages 9, 9 by the influence of the gravity. Accordingly, proper quantities of lubricating oil can be distributed to the first and second through-holes 11 and 12 respectively.
Though not shown, German Patent No. 2844995 discloses an oil air lubricating apparatus in which a proper quantity of lubricating oil fed into a distributor communicated with one oil supply passage is distributed to a portion to be lubricated and the residual quantity of lubricating oil is distributed to the next distributor. In the structure disclosed in German Patent No. 2844995, therefore, a plurality of first intermediate passages to be communicated with portions to be lubricated and a plurality of second intermediate passages to be communicated with next distributors are opened alternately in places arranged circumferentially in the inner circumferential surface of the distributor communicated with the oil supply passage. According to the oil air lubricating apparatus disclosed in German Patent No. 2844995 and configured as described above, proper quantities of lubricating oil can be distributed without imbalance in any intermediate passage even in the case where the quantity of lubricating oil fed to the distributor is so small that the lubricating oil is reserved in the lower portion of the distributor by the influence of the gravity.
In the oil air lubricating apparatuses disclosed in the Japanese Patent Publication No. Hei. 5-340499 and German Patent No. 2844995, a complex structure is required in order to supply proper quantities of lubricating oil to portions to be lubricated respectively. Accordingly, increase in production cost cannot be avoided. Further, in the case where the number of portions to be lubricated is not smaller than three, distributors not smaller than two are required. Further, while the distributors are assembled in the inside of the support hole provided in the housing, it is necessary to make the positions of openings of the branch passages provided in the support hole and the positions of oil-discharge openings of the distributors coincident with each other. Accordingly, not only an exclusive-use jig for assembling the distributors is required but also the labor required for the assembling work is considerably troublesome.